The present invention relates to an observing method and its apparatus, using a scanning electron microscope, for reviewing a defect that occurs on a surface of a semiconductor electronic circuit substrate, a liquid crystal display substrate or other substrates.
In a manufacturing process of a large scale integrated circuit including a semiconductor electronic circuit substrate and a liquid crystal display substrate, in order to achieve an early increase in yield and stable operation of the manufacturing process, it is important to grasp situation of how a defect has generated by using an inline wafer inspection system, and to analyze the defect in detail by an analyzer, and thereby to take quick and appropriate measures for the manufacturing process on the basis of knowledge concerning cause of the defect generation acquired from the above. An inline wafer inspection apparatus outputs coordinates of the defect; and the analyzer acquires (collects) a defect image on the basis of the defect coordinates. An engineer identifies the cause of the defect on the basis of the defect image. An example of the analyzer mentioned above includes a review SEM apparatus which acquires (collects) a high-definition image by use of a scanning electron microscope (SEM). The review SEM is characterized by having an automatic defect review (ADR) function of acquiring a defect image using defect coordinates, and an automatic defect classification (ADC) function of classifying the acquired image according to a kind of a defect. In recent years, with the progress of the miniaturization of semiconductor processes, the number of defects detected in inline wafer tends to increase. Therefore, the speedup of the ADR is becoming more and more important.
On the other hand, in order to analyze a defect in further detail, in addition to an image taken from just above (a perpendicular direction) a target to be observed (hereinafter this image is abbreviated as “perpendicular observation image”), performing tilt observation is also effective. As the tilt observation, Japanese Patent Laid-open Nos. 2000-21345 and 2004-219343 disclose stage tilt in which observation is made in an oblique direction by tilting a stage.
Further, as a tilt observation method, U.S. Pat. No. 6,812,462 describes a configuration in which two electro-optical systems, a dedicated electro-optical system for imaging a perpendicular observation image and a dedicated electro-optical system for performing tilt observation, are used in combination.
Since the stage tilt described in the Japanese Patent Laid-open Nos. 2000-21345 and 2004-219343 needs to tilt the hardware of a stage. Accordingly, if a perpendicular observation image and a tilt observation image are acquired on a defect basis, it is necessary to tilt the hardware on a defect basis. Therefore, the above tilt observation method is not suitable for ADR which requires acquisition of many images at high speed. Heretofore, high-speed acquisition of a tilt observation image concurrently with a perpendicular observation image during ADR was not sufficiently taken into consideration.
On the other hand, the configuration described in U.S. Pat. No. 6,812,462, which uses the two electro-optical systems in combination, has a problem in that imaging tilted in an arbitrary direction cannot be performed. Therefore, this configuration is not suitable for defect review in which it is important to take a tilt observation image from an arbitrary direction.